Desulfurization process employing a complex of metal of groups i-a,iii-b,and the lanthanide series



May 6, 19

Filed June 23, 1966 DESULFURIZATION 69 I c. L. ALDRIDGE 3,442,797 DESULFURIZATION PROCESS EMPLOYING A COMPLEX OF METAL OF GROUP I-A, III-B AND THE LANTHANIDE SERIES Sheet oi 3 DESULFURIZATION WITH POTASSIUM REAGENTS I I I I I I I I I I 0 K28 Q KOH-TEXAS FEED L K$b03 IKOH-KUWAIT FEED 'IIII'II o 2 3 4 5 e MOLES H o/2K FIGURE I CLYDE L. ALDRIDGE Inventor Attorney May 6, 1969 c. L. ALDRIDGE 3,442,797

' DES'JLFURIZATION PROCESS EMPLOYING A COMPLEX OF METAL 0F GRQUP I-A, III-B AND THE LANTHANIDE SERIES I Filed June 23, 1966 Sheet v43 1 of 5 DESULFURI ZATION WITH CESIUM HYDROXIDE COMPARED TO POTASSIUM REAGENTS OF FIG. I

-'-POTAS$|UM REAGENTS C CsOH 2 Q 30- 1 '3 0: D :1 D 20- (I) g Y 1 l0 I \J' 0 l 2 3 4 5 6 T 8 9 IO MOLES H O/ZCS 9 FIGURE 2 CLYDE L. ALDRIDGE At tor ney May 6, 1 969 c. ALDRlD G E I 3,442,797

DESULFURIZATION PROCESS EMPLOYING A COMPLEX OF METAL OF GROUP I-A, III-B AND THE LANTHANIDE SERIES Filed June 25, 1966 Sheet 3 of 3 DESULFURIZATION WITH Di COMPARED TO POTASSIUM REAGENTS OF F|G.l

0 AND Y2 0 0 I s I M '9 E G a l R M I |U| i? m 0 $32 16 .wDYL AI. 5 s i 4 I 3 I: I A

MOLES H2O/2 9 FIGURE 3 CLYDE L. ALDRIDGE Attorney United States Patent U.S. Cl. 208-243 8 Claims ABSTRACT OF THE DISCLOSURE Desulfurization of high boiling petroleum fractions is accomplished by the use of metal hydrates or complexes with water in which one molecule of water is bound to two metal cations chosen from the groups consisting of Groups I-A, III-B and the lanthanide series. Water vapor may be added as needed to maintain the critical complex ratio.

This invention relates to an improved process for removing sulfur, nitrogenous and metallic contaminants from heavy petroleum fractions. More particularly the invention relates to the use of critical amounts of water in conjunction with metal salts employed in the desulrization of high boiling petroleum feedstocks.

Generally, sulfur occurs in petroleum stocks in one of the following forms: mercaptans, sulfides, disulfides, and as part of a more or less substituted ring, of which thiophene, benzothiophene, and dibenzothiophene are prototypes. The mercaptans are generally found in the lower boiling fractions, e.g. a naphtha, kerosene, and light gas oil. Numerous processes for sulfur removal from these lower boiling fractions have been suggested, such as doctor sweetening (wherein mercaptans are converted to disulfides), caustic treating, solvent extraction, copper chloride treating, and so forth, all of which give a more or less satisfactory decrease in sulfur or inactivation of mercaptans by their conversion into disulfides. When the process results in the latter effect, the disulfides generally remain in the treated product and must be removed by another step if it is desired to obtain a sulfur-free product.

Sulfur removal from higher boiling fractions, however, has been a much more difficult operation. Here, the sulfur is present for the most part in the less reactive forms as sulfides, disulfides, and as a part of a ring compound, such as substituted thiophenes. Said sulfur, of course, is not susceptible to chemical operations satisfactory for removal of mercaptans. Extraction processes employing sulfur-selective solvents are also'unsatisfactory because the high boiling fractions contain a much higher percentage of sulfur-containing molecules; for example, even if a residuum contains only about 3% sulfur, it is estimated that substantially all the molecules may contain sulfur. Thus, if such a residuum were extracted with a solvent selective to sulfur compounds, the bulk of the residuum would be extracted and lost.

Metallic contaminants, such as nickel and vanadium compounds, are found as innate constituents in practically all crude oils associated with the high Conradson carbon asphaltic and/or asphaltenic portion of the crude. When the crude oil is topped to remove the light fractions boiling below about 450650 F., the metals are concentrated in the residual bottoms. The residual bottoms may also contain nitrogen compounds.

A process for the chemical desulfurization, demetallization and denitrogenation of residuum stocks employing fused alkali metal hydroxides has been disclosed by Mattox in US. Patent 3,164,545, issued Jan. 5, 1965.

The Mattox patent indicates that the amount of water 3,442,797 Patented May 6, 1969 in the molten alkali metal hydroxide is important. I have found that a certain critical water content is the key to catalytic activity for a very large group of metal salts which have been considered for use as desulfurization agents.

By using the concept of the present invention it is possible to precisely predict the conditions of optimum activity for a wide variety of reagents and this is the object of the invention.

Generally speaking the object of the invention is achieved by contacting the sulfur-containing high boiling petroleum feedstocks with a metal salt complex in which the composition of the complex is essentially one molecule of water for each two positive charges on the metal ion. As far as it is possible this precise ratio is maintained throughout the desulfurization reaction.

For purposes of this specification and claims the term metal salt complex means a metal salt having a hydrated cation which may be illustrated as shown below:

The most preferred alkali metal is potassium and the hydrated potassium salt can be shown as:

It should be understood that the molecule of water complexed with the metal salt is complexed with the metal, i.e., the cation and not with the anionic element of the salts. Many salts are hydrated and have water associated with the anion. The water associated with the anion may or may not dissociated from the anion under reaction conditions. If it does not the desulfurization reagent as a whole will contain more than the critical amount of water, but the excess water will not be complexed with the cation and will notatfect the criticality of the reaction.

In another preferred embodiment the metal is a rare earth metal such as yttrium, lanthanum, thorium, cerium, praseodymium, neodymium, etc, and mixtures of these in pure or in impure form, e.g. concentrated rare earth ores. Commercially available rare earth ores include monazite, bastnasite, yttrialite, lanthanite and didymium concentrates. Thus the Group III-B metal salts, particularly the Group III-B metal oxides provide excellent desulfurization, denitrogenation and metal removal agents upon hydration with the proper amount of water. If desired the Group III-B metal oxides can be supported on a suitable carrier such as alumina, silica alumina, zeolites, etc.

The feed to the process is a high boiling petroleum feedstock which contains from 50-100 vol. percent of materials having a boiling point higher than 500 F.

Suitable high boiling petroleum feedstocks include heavy whole crude oils, atmospheric residuum, vacuum residuums, visebreaker bottoms, deasphalted oils, refinery cycle stocks, and shale oil. When required, very viscous oils can be cut back or diluted to a suitable viscosity or gravity with a light diluent oil so that they can be intimately contacted with the treating agent. Oils containing 0.5 to 10 wt. percent sulfur, preferably 1 to 6 wt. percent sulfur, can be processed to remove about 1070% of the sulfur in single stage treats.

The feed is contacted in any suitable reaction vessel, preferably a vessel lined with a corrosion resistant material. Contacting may be in the form of a moving slurry or in a fixed bed.

The ratio of metal salt complex to feed is 10 to 300 wt. percent, preferably 25-150 wt. percent, based on the feed. The time of contacting can vary from 10 minutes to 20 hours. Temperatures ranging from 300 to 1000 F., preferably 500-800 F. and pressures ranging from 0.1 to 1000 p.s.i.a. are employed.

The water of hydration may be added to the reactor together with the reagent, i.e. via a prehydration, or may be added separately and the hydration allowed to occur under reaction conditions. Sufiicient water vapor pressure is maintained under reaction conditions to keep the treating agent at equilibrium in the desired degree of hydration, i.e., 1 H O per 2 in the reagent cation.

The invention will be more completely described with reference to the following examples and with reference to the drawings which consist of graphical correlations of desulfurization runs with a number of metal salt complexes. FIGURE 1 depicts the desulfurization activity of a group of potassium salts. FIGURE 2 compares the desulfurization activity of a cesium salt compared to the potassium salts. FIGURE 3 compares the desulfurization activity of a group of rare earth salts with the activity of the potassium salts.

Referring to FIGURE 1 the desulfurization activity of such diverse compounds as potassium sulfide, potassium hydroxide, potassium antimonate and potassium aluminate is correlated. The runs were on West Texas atmospheric residuum at 650 F. for 4 hours and on Kuwait vacuum residuum at 600 F. for four hours. Moles of water per 2K are compared to desulfurization (percent). It can be seen that the curve peaks sharply at one water molecule per two potassium ions. Desulfurization at this point exceeds 40%.

Data for three metal salts are set forth below in tabular form. Assuming it is desired to operate within 20% of the maximum activity of any of the metal salts, i.e., above 35% desulfurization as compared with 42% maximum activity under the conditions employed, the data show it is essential to operate within very narrow ranges of water content in the metal salt complex. The data also bring out the fact that the optimum narrow ranges differ widely for the various reagents with respect to weight percent of H based on the total reagent.

4 Thus, if potassium antimonate is the metal salt employed for desulfurization the water content of the complex cannot vary more than about 1.0 wt. percent if over 35% desulfurization is the goal. Similar critical water contents are required for K Al O and KOH.

It is also important to note that with a given reagent the optimum quantity of water can change as the reagent becomes spent. Assuming KOH as the reagent, the reaction is:

The optimum H O for KOH is 13.85 wt. percent, but by the time the reagent is nearly spent this optimum has changed to 12.6% due to the fact that K S is a reactive agent having a different water optimum. Thus if the water content is maintained at the original optimum (13.85%) throughout the life of the catalyst the desulfurization activity will be 38% rather than 42%.

Although it was formerly appreciated that water content is an important factor in obtaining good desulfurization activity from KOH, it was not appreciated that the relationship was critical and that differing critical water contents are required for other metal salts, based on the metal salt complex comprising one molecule of water for each two positive charges on the metal ion.

That the concept is valid for alkali metal compounds other than potassium compounds is shown by the following set of experiments with cesium hydroxide. West Texas atmospheric residuum containing 1.3% sulfur and preoxidized to 0.5% oxygen content was treated at 500 F. for 4 hours in a stirred autoclave with cesium hydroxide (22 wt. percent on an anhydrous basis). In each case the cesium hydroxide was hydrated to the indicated degree before charging to the reaction.

TABLE II filo/2 cs 0.07 0.48 1.00 2.40 Wt. percent H10 in 05011 (based on total CSOH-l-HzO) 0.42 2.80 6.15 12.6 Percent Desulfurization 10 19 21 11 TABLE III Run Number 19 45 29 31 Metal Oxide Hydrate LazOa YzOa C010: D zoa (Didymium) Water In Hydrate (Wt. percent).- 14. 3 24. 9 34. 0 21. 0 Feed Sulfur (Wt. percent). 5. 26 5. 26 5. 26 5. 26 Product Sulfur (Wt. percent). 4. 48 4. 62 4. 82 4. 69

As charged.

FIGURE 3 compares desulfurization results for La O Di O and Y O with potassium salt hydrates. Again, maximum desulfurization for both types of treating agents occurs at a degree of hydration equal to one H O for two positive charges on the reagent cation.

Similar results are obtained with thorium oxide hydrates, iron oxide hydrates, tunsten oxide hydrates, manganese oxide hydrates, cobalt oxide hydrates, molybdenum oxide hydrates and vanadium oxide hydrates.

Thus hydrated salts of metals of Groups I-A, III-B, V-B, VII-B, VII-B, V I I-I-B and the lanthanide series are suitable. Hydrated salts of metals of Groups il-A and I l'I-B are preferred.

The treating agent is regenerated for reuse by appropriate means known in the art. For example, iron manganese, and molybdenum oxides are regenerable by roasting and rehydnation. Groups LA and III-B oxides and hydroxides are regenerable by high temperature steaming. The potassium salts are regenerable by calcination followed by rehydration.

What is claimed is:

1. Process for removing sulfur from 'a high boiling petroluem feedstock which contains from 50-100 vol. percent of materials having a boiling point higher than 500" F. and which contains 0.5 to 10 wt. percent sulfur comprising the steps of contacting the feedstock with 10-300 wt. percent of a complex of a compound of a metal chosen from the group consisting of Groups I-A, :lI I-B and the l-anthanide series in which the composition of the complex is essentially one molecule of water for each two positive charges on the metal ion, separating the treated petroleum from the complex and recovering petroleum of reduced sulfur content.

2. Process according to claim 1 in which the metal salt complex contains a metal of Group I-A of the Periodic Table.

3. Process according to claim 1 in which the metal of the metal salt complex is potassium.

4. Process according to claim 1 in which the metal of the metal salt complex is cesium.

5. Process'according to claim 1 in which the metal salt complex contains a metal of Group llII-B of the Periodic Table.

6. Process according to claim 1 in Which the metal salt complex contains a metal of the lanthanide series of the Periodic Table.

7. Process according to claim 1 in which the metal salt complex is obtained by hydration of a rare earth ore.

8. The process according to claim 1 in which sufficient water vapor is added separately to keep the metal compound complex at equilibrium at the required degree of hydration.

References Cited UNITED STATES PATENTS 1/1965 Mattox 208230 US. Cl. X.R. 

